It is recognized that progression of such diseases as cancer and atherosclerosis, for example, and other debilitating disorders including neurodegenerative disease and osteoarthritis, is accompanied by changes in stiffness of biological tissue. Recent advances in the field of mechanobiology establish that these changes in the stiffness of the extra-cellular matrix (ECM) are not merely passive consequences of earlier causal events, but may in turn influence the behavior of tissue cells, thereby possibly further exacerbating the disease. The biological cells are mechanosensitive in that they feel, perceive, and respond to the mechanical properties of their ECM microenvironment. For example, a cell senses stiffness by exerting tension as it anchors and pulls on the ECM via focal adhesion sites that involve transmembrane integrins and a network of intracellular mechanosensory proteins. Mechanical cues received from the ECM are relayed and translated by intracellular signaling pathways that, in turn, influence cell morphology, differentiation, proliferation, contractility and elasticity. Behavior of the cells that have been altered affects a dynamic balance between the ECM production and break down, thereby causing the ECM stiffness to be changed further. As a result, a positive feedback loop is established with consequences that are sometimes detrimental to the cell's health. For example, the altered ECM stiffness can induce epithelial tumor progression, switch on the malignant phenotype in tumor cells, cause smooth muscle cell proliferation in atherosclerosis, enhance the angiogenesis potential of endothelial cells, initiate calcium deposition by interstitial cells in cardiac valves, modulate stem cell differentiation, and induce cell apoptosis. The cellular response was shown to be regulable via tuning the ECM mechanical properties to values comparable with those of a normal tissue.
Changes in the mechanical properties of the ECM may provide the early detectable signs of the disease onset that likely precede aberrant intracellular signals. Moreover, by engineering the ECM mechanical properties it may be possible to reverse the progress of the disease. Therefore, the capability to measure and monitor minute changes in the ECM stiffness at the size scale sensed by cells (referred to herein as cellular spatial scale) is vital in advancing current understanding in mechanobiology and may, quite possibly, enable not only the detection of the initial onset of a number of critical diseases but also the guidance of an early therapeutic intervention in case of such diseases.
The currently used systems and method are adapted to in vitro studies that evaluate the impact of global (or bulk) ECM mechanical properties on condition of the cells. In contradistinction, however, the biological cells probe the stiffness of their local microenvironment on a substantially smaller scale, via micron-sized focal adhesions and, due to tissue heterogeneities and matrix remodeling, the ECM micromechanical environment that a cell perceives is vastly different from the bulk mechanical environment. The majority of the hypotheses in mechanobiology, generated from experiments in monolayer cell models, fail to recapitulate the complex three-dimensional (3D) environment that a cell experiences in vivo. It is well established that cellular behavior is profoundly different in 3D models where the influence of the ECM composition and stiffness is far more complicated compared to the two-dimensional (2D) monolayer models. Accordingly, there remains a question of how mechanobiological relationships translate into biologically relevant 3D disease models and in clinically relevant systems in vivo. However, no means exists today that enable measurements of the ECM stiffness in 3D at microscopic size scales relevant to the microenvironment of a biological cell. The present invention offers such means.